Various kinds of aromatic copolyamides or aromatic aliphatic copolyamides, disclosed in the prior art are known to be random copolyamides which have no regular block unit sequence in their molecular structure, since all of them are prepared from the mixture of more than two kinds of diamines or diacidhalides ("Aramid Fiber," Kirk-Othmer Encyclopedia of Chemical Technology, 3rd ed., vol. 3,213-242 (1978), John Wiley & Sons, Inc.). Therefore, it is clear that with any of the conventional art, the polymers having a regular unit sequence of molecular structures can not be made.
This invention is based on a successful synthesis of an extremely pure pre-polymer, N,N'-bis(4-aminophenyl)terephthalamide, having the following structure. ##STR6##
The aromatic diamine (Compound I) is a "polymer block" of poly(p-phenylene)terephthalamide and can be prepared from aniline and dimethyl terephthalate by sequence of organic synthesis, such as, condensation, nitration and hydrogenation.
This important object of the invention, therefore, is to provide various kinds of wholly aromatic or aliphatic aromatic block copolyamides which have an absolutely regular block unit sequence in the skeleton thereof.
Another object of the invention is to provide N,N'-bis(4-aminophenyl)terephthalamide which is used as a polymer block in preparing the polyamides of the invention.
Still another object of the invention is to provide a process for preparing the polyamides and the polymer block.
These and other objects and advantages of the invention will be more apparent by the description hereinafter without deviating from the true scope of the invention.